1. Field of the Invention
The present invention relates to a method of manufacturing an outside ring and, more particularly, is directed to a method for the manufacture of an outside ring for use in a synchromesh mechanism of a manual transmission for automobiles.
2. Related Background Art
Recent increases in output power of automobile engines have given rise to a need for greater synchromesh capacity of manual transmissions.
To increase the synchromesh capacity, a double cone type synchromesh mechanism instead of a single cone type has been proposed, so as not to increase the operating force of the shift lever.
As shown in FIG. 20, a double cone type synchromesh mechanism has a construction wherein an outer balk ring 4, an outside ring 5, and an inner balk ring 6 are provided between the coupling sleeve 1 and the clutch gear 3 which rotates in synchronism with the transission gear 2. The coupling sleeve 1, being engaged with the insert spring 12 fitting onto the periphery of the synchronizer hub 8 which rotates with the drive shaft 7, moves axially (left/right direction in FIG. 20) on the basis of an operation of the shift lever.
When the coupling sleeve is pushed to left in FIG. 20 with the shift lever operation, due to the action of the frictional force between the outer balk ring 4 and the outside ring 5 and between the outside ring 5 and the inner balk ring 6, any difference of revolution between the coupling sleeve 1 and the clutch gear 3 is eliminated. Then, a spline 9 on the inner periphery of the coupling sleeve moves so as to bridgingly couple a spline groove 10 formed on the outer periphery of the clutch gear 3 and a spline groove 11 formed on the outer periphery of the insert spring ring 12, whereby the transmission gear 2 rotates in synchronism with the drive shaft 7.
The outside ring 5, in a double cone type synchromesh mechanism constructed and operated as above described has a configuration as in FIGS. 21 and 22.
More particularly, the outside ring 5 comprises a tapered cylinder portion 13 whose diameter changes along its axis and several projections 14 which are formed at regular intervals on the end surface 13a of larger diameter. The thickness t of each projection 14 is smaller than the thickness T of the tapered cylinder portion 13 (T&gt;t), and the projection 14 are bent inwardly with regard to the cylinder portion 13 so as to be parallel to the axis of the cylinder portion 13.
An outside ring 5 of such configuration as described has been produced traditionally by two methods. The first method involves removing the unnecessary portions of a thick walled tubular material in a machining or milling process. The second method involves removing the unnecessary portions of a blank 15, such as shown in FIGS. 23 and 24, which has been forged out of a bar material with a fixed length.
When making an outside ring in accordance with either of the above mentioned traditional methods, production cost is very high.
In case of the first method, the portion to be cut is so large that the yield is very poor and a lot of machining time is required.
The second method requires many forging processes to produce a blank 15 as is shown in FIGS. 23 and 24. Also, since a large portion has to be cut, the yield is poor and substantial machining time is required.